Alternative Names

How the test is performed

You will wear a hospital gown or clothes without metal snaps or zippers (such as sweatpants and a t-shirt). Some types of metal can cause blurry images.

You will lie on a narrow table that slides into a large tunnel-like tube.

Some exams require a special dye (contrast). Most of the time, you will get the dye through a vein (IV) in your hand or arm before the test. You can also get the dye through an injection. The dye helps the radiologist see certain areas more clearly.

During the MRI, the person who operates the machine will watch you from another room. The test most often lasts 30-60 minutes, but may take longer.

How to prepare for the test

You may be asked not to eat or drink anything for 4 - 6 hours before the scan.

Tell your doctor if you are afraid of close spaces (have claustrophobia). You may be given a medicine to help you feel sleepy and less anxious. Your doctor may suggest an "open" MRI, in which the machine is not as close to the body.

What the risks are

MRI contains no radiation. There have been no reported side effects from the magnetic fields and radio waves.

The most common type of contrast (dye) used is gadolinium. It is very safe. Allergic reactions to this dye are rare. However, gadolinium can be harmful to people with kidney problems that need dialysis. If you have kidney problems, please tell your health care provider before the test

The strong magnetic fields created during an MRI can cause heart pacemakers and other implants to not work as well. It can also cause other pieces of metal inside your body to move or shift. For safety reasons, please don't bring anything that contains metal into the scanner room.

References

Chou R, Qaseem A, Owens DK, Shekelle P; for the Clinical Guidelines Committee of the American College of Physicians. Diagnostic Imaging for Low Back Pain: Advice for High-Value Health Care From the American College of Physicians. Ann Intern Med. 2011 Feb 1;154(3):181-189.